VDD is the supply voltage for the control electronics, and can be between 4.5 V and 30 V. The VDD quiescent current is 8 mA.

VS is the supply voltage for the output stage (TEC), and can be between 3 V and 30 V. The VS quiescent current is 8 mA.

You need to balance the output compliance voltage with the internal power dissipation in order to decide whether or not to separate VDD and VS but it is a wide range to work within. Design considerations:

The compliance voltage for the TEC is approximately 0.5 V less than the supply voltage. If the supply voltage in your system is a low value, perhaps 5 V, the maximum compliance voltage will be about 4.5 V. That may limit the power you can drive to the TEC, so you might want to separate VDD and VS and use a higher voltage for VS.

If the supply voltage in your system is a higher voltage, perhaps 12 – 15 V, the power dissipation in the output stage of the WTC3243 may be too high – again, check the SOA. If that’s the case you’ll need to separate VDD and VS and use a lower voltage for VS.

Using a single supply for VDD, VS, and the other electronics in the system may lead to increased noise in the laser output. If you use a dedicated supply for VS, you can keep the electronics noise isolated from the laser current source, and reduce laser output noise.

As always, if you have questions about configuring your WTC3243 call the factory for prompt and free technical assistance.